NEW YORK -- And just like that, Georges St-Pierre is back -- and a two-weight UFC champion.

Stepping back into competition for the first time since 2013, St-Pierre (26-2) submitted Michael Bisping in the third round of the middleweight title fight on Saturday, which headlined UFC 217 inside Madison Square Garden.

The finish came at the 4:23 mark, moments after St-Pierre floored Bisping (30-8) with a left hook. The Canadian star threw hard punches from the top, before jumping to Bisping's back and applying a rear-naked choke. Bisping refused to tap and went unconscious.

Georges St-Pierre locked in a rear-naked choke on champion Michael Bisping in the third round. The fight was stopped at 4:23 when Bisping went unconscious from the hold. Jeff Bottari/Zuffa LLC/Getty Images

It is St-Pierre's 20th career win in the UFC, moving him into a tie with Bisping on the UFC's all-time list. He also becomes the fourth multidivisional champion in UFC history; he held the welterweight belt from 2008 to 2013, as well.

"I don't have words in my mouth right now," St-Pierre said. "It's a dream come true. He hurt me very hard. I got stunned and tried to hide it. I wouldn't like to do that fight again."

Bisping, 38, who won the title in stunning fashion in June 2016, did not offer an excuse for the loss.

"You've got to give it up to Georges, he was the better man tonight," Bisping said. "New York, I came and fought my ass off. I tried to be entertaining. Georges was the better man. Hell of a f---ing squeeze he's got."

Prior to UFC 217's main event between Michael Bisping and Georges St-Pierre, a multitude of undercard fights had major implications. Here's how it went down.

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The longest-reigning welterweight champion in the sport's history, St-Pierre walked away from the sport in late 2013, citing his need for a break and the lack of an effective drug-testing system in the sport. The UFC added a comprehensive, year-round drug testing system in 2015.

St-Pierre did not show strong signs of the layoff against Bisping. According to Fightmetric, he outlanded Bisping in total strikes 74-58 and converted all three of his takedown attempts.

It was by no means an easy fight for St-Pierre, however. Although he was successful in getting Bisping to the ground, he struggled to keep him there. And in the third round, Bisping actually opened a cut on the bridge of St-Pierre's nose with good elbow work off his back.

In the second round, Bisping started to neutralize St-Pierre's jab and find a home for his right hand. It seemed Bisping was getting the better of the striking, until St-Pierre landed the fight-changing left hook.

"We knew he had problems with shots coming from his right," said St-Pierre, who worked with boxing trainer Freddie Roach during his camp. "Our plan was to fake him on his left side to attract his attention and strike him on the right. That's what we did most of the fight."

Before Saturday, St-Pierre said he is contractually obligated to defend the middleweight title. His obvious challenger is Robert Whittaker, who won an interim title by defeating Yoel Romero last summer. The UFC has announced an event in February in Perth, Australia. Whittaker trains out of Sydney.